An IPTV transmits messages including television, video, text, graphics, data and so on over an IP network, and provides a manageable multimedia service of quality of service/quality of experience (QoS/QoE for short) assurance, security, interaction and reliability. That is, the IPTV is a manageable multimedia service needing the QoS and security assurance, which is obviously different from those uncontrollable and unmanageable stream media applications with no assurance in the QoS and security on the Internet.
A real time streaming protocol (RTSP for short) defines how a one-to-multiple application program effectively transmits multimedia data over the IP network, sets up and controls one or more time-synchronous continuous stream media, such as audio and video. The RTSP is above a real-time transport protocol (RTP for short) and a real-time transport control protocol (RTCP for short) in the architecture and provides a network remote control function for multimedia servers.
As shown in FIG. 1, an IPTV system includes a media location service system (MLSS for short) and nodes, wherein the MLSS is used for monitoring the number of orders of each node; and the node is actually a universal service server (USS for short) including a service module, an adaptation module, a database module and a media distribution unit (MDU for short). The nodes are classified into a central node and an edge node, and the difference between them is that contents to be distributed are normally provided and stored on the central node, then distributed to the edge node by using a distribution technology. Obviously, for the IPTV system, the central node and the edge node are different in function, and how to relieve the load of the central node to balance the network load has become an important task.
At present, there are two ways for network load balancing:
1) global service load balancing (GSLB for short)
A request of a user is directed to a nearest node within the scope of the whole network, and the main characteristic of the GSLB lies in a proximity determination.
2) local service load balancing (or service load balancing, SLB for short)
This way is limited to a certain area, aiming at searching for a most suitable node within a specific area to provide services. The decisions of the local service load balancing are made mainly based on running status such as health, load situation and supported media format of a node.
Neither of the two ways above solves the problem of balancing load of a channel (for example, a channel has a high order rate).